Methane extinction is a very real phenomena… unfortunately. The clathrate gun hypothesis is the popular name given to the hypothesis that rises in sea temperatures (and/or falls in sea level) can trigger the sudden release of methane from methane clathrate compounds buried in seabeds and permafrost which, because the methane itself is a powerful greenhouse gas, leads to further temperature rise and further methane clathrate destabilization — in effect initiating a runaway process as irreversible, once started, as the firing of a gun. The best example (or worst) is the Permian extinction event, when 96% of all marine species became extinct 251 million years ago.